Hydrothermal Power Plant

ABSTRACT

A super critical water oxidation reactor (SCWOR) serves as an extremely efficient power source in a power plant by coupling the various output streams in thermal communication with multiply staged or cascaded compressor-expanders that are themselves mechanically coupled to a motor or generator. In one embodiment heat from re-circulating liquid brine loop either directly or indirectly preheats the exhaust gases of the SCWOR prior to expansion. In another embodiment the heat of compression is used to preheat the effluent of an expander prior to a subsequent expansion stage. The re-circulating brine loop also preferably preheats expander effluent prior to a subsequent expansion stage.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation-in-part of and claims the benefit of priority to the international patent application of the same titled filed on Apr. 27, 2010, having application serial no. PCT/2010/US032608, which is incorporated herein by reference.

The present application also claims the benefit of priority to the US Provisional patent application of the same titled filed on Apr., 28, 2009, having application Ser. No. 61/173,498, which is incorporated herein by reference.

BACKGROUND OF INVENTION

The present invention relates to an improved means of electric power generation via the oxidation of various organic materials in a Supercritical Water Oxidation Reactor (SCWOR).

Prior methods of using SCWOR to generate electric power are disclosed in the following U.S. Pat. No. 5,485,728, U.S. Pat. No. 5,000,099 and U.S. Pat. No. 7,640,745, which are incorporated herein by reference.

SCWOR have an inherent utility as the most of efficient means to completely oxidize organic waste of all types, including toxic chemical, as well as wet biomass, such as sludge.

However, while an SCWOR can also use conventional fuels without creating harmful by-products, other than CO2, the conventional fuels need not be heavily refined and can even be contaminated with water, organic and organo-inter-metallic and metallic compounds.

However, prior to the current invention, SCWOR have had poor efficiencies that have not made commercially viable to produce energy. Accordingly, the actual implantation of SCWOR designs in the patent literature is scant and largely in academic research laboratories and government end use to date.

Biofuels, in particular ethanol, has gained popularity as an automotive gasoline additive in the US, as well as a direct fuel in other countries. AS ethanol is generally produced from corn or such cane, a significant non-fermentable biomass is created in these processes. These biomasses are sometimes burnt as fuel, but being somewhat wet, are an inefficient and particulate polluting heat source.

It would be desirable to utilize mixed biomasses of varying water contents as a fuel with the utmost efficiency to produce power with an entirely clean combustion process, which is producing CO2 as the only gaseous by product, other than water as steam. Achieving such an objective would reduce the dependence on fossil fuels and reduce the overall “carbon footprint” of power production by turning biomass that might otherwise be burnt without generating power into power. In addition, such an improvement in technology would facilitate the clean up and disposal of toxic wastes and allow safe disposal of waste at many manufacturing facilities without the expense and risk of storing and transporting waste.

It is therefore a first object of the present invention to provide such a SCWOR of improved efficiency in which moist organic materials can be efficiently combusted without expending additional energy to pre-dry the fuel, and without chemical conversion of the wet fuel into another fuel that is more suitable for combustion in existing combustion apparatus.

It is a further object of the invention to provide such power plant in which the SCWOR provides complete combustion without undesirable by-products.

It is still another object of the invention to provide such a plant is capable of accept multiple and diverse fuel sources for the recovery of useful energy with high thermal efficiency.

SUMMARY OF INVENTION

In the present invention, the first object is achieved by providing a power generating plant that comprises a super critical water oxidation reactor (SCWOR) having a feed port for reactants and an exit port for exhaust, a brine separator having an inlet for receiving the exhaust of the SCWOR and at least one outlet for gases, two or more pairs of air compressors and expanders coupled in rotary motion by a common axle, at least one heat exchanger associated with each of said one or more pairs of compressors and expanders, wherein the hot exhaust gas exiting the brine separator enters a first expander, and the cooled exhaust gas exiting the first expander enters a first heat exchanger that cools hot compressed air from the air compressor while reheating the cooled exhaust gas exiting the first expander prior to a second stage of expansion, and the cooled air exiting the heat exchanger enters a downstream compressor stage in said 2 or more pairs of air compressor and expanders, a motor or motor/generator with a rotary coupling to at least one common drive mechanism of the air compressor-expander pairs, wherein the rotary motion of the drive mechanism supplies mechanical power driving the motor generator for both electric power and driving the air compressors.

The above and other objects, effects, features, and advantages of the present invention will become more apparent from the following description of the embodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram the generically discloses the operative principles of the HTPP in a first embodiment.

FIG. 2 is a schematic diagram of the power generation system in the HTPP of FIG. 1.

FIG. 3 is a schematic diagram of a second embodiment of the HTPP.

FIG. 4 is a schematic diagram of a third embodiment of the HTPP.

FIG. 5 is a schematic diagram of a fourth embodiment of the HTPP.

FIG. 6 is a schematic diagram of a fifth embodiment of the HTPP.

FIG. 7 is a schematic diagram of a sixth embodiment of the HTPP.

FIG. 8 is a schematic diagram of a seventh embodiment of the HTPP.

FIG. 9 is a schematic cross-sectional elevation view of a gravity separator for use with any of the above embodiments.

DETAILED DESCRIPTION

Referring to FIGS. 1 through 9, wherein like reference numerals refer to like components in the various views, there is illustrated therein a new and improved Hydro-Thermal Power Plant (HTPP) generally denominated 100 herein.

In accordance with the present invention, FIG. 1 illustrates a HTPP 100 that comprises a super critical water oxidation reactor (SCWOR) 110. At the super critical conditions the organic materials that enter the SCWOR 110 are oxidized, as are described for example in U.S. Pat. Nos. 5,558,783 (issued to McGuinness on Sep. 24, 1996) and 5,384,051 (issued to McGuinness on Jan. 24, 1995), which are incorporated herein by reference. This oxidation reaction generates heat that is used to generate electrical power in the HTTP 100 as described further below. The SCWOR 100 preferably incorporates a permeable-wall or transpiring wall 115. The SCWOR 110 may be operated at pressures above or below the critical pressure or water.

In a currently preferred mode of operation, various combinations of biomass and organic materials are co-injected with water or in an aqueous suspended state into the top of the SCWOR 110 at the injector 1405. Hot exhaust and reaction products from the SCWOR 110 are controllably cooled in the quench cooler 120 by direct mixing with cooled re-circulated brine that circulates in line 1300 from the bottom of the gravity separator 130. Gravity separator then received this cooled reaction product from the quench cooler 120 via inlet portal 131. Thus, the gravity separator 130 receives the output of the SCWOR 100 after passing through the quench cooling section 120.

It should be appreciated that an important aspect of the current invention is the extraction of heat from the hot liquid recirculation stream of the brine in line 1300. This is both a more efficient way to extract and more effectively deploy heat from gases as proposed in U.S. Pat. No. 5,485,728 (which issued to Norman L. Dickinson on Jan. 23, 1996 for “EFFICIENT UTILIZATION OF CHLORINE AND MOISTURE-CONTAINING FUELS”) and U.S. Pat. No. 5,000,099 (which is a continuation in part of a series of patents to Dickinson), and also enables other routes for heat and energy recovery that would otherwise be lost in a prior art system. Other important and alternative aspects of the invention are described further below.

This technology can be applied to all types of pumpable organic sludge and raw biomass slurries. A process using a waste water treatment facility (WWTF) sludge is now described for illustration purposes, as it will be apparent to one of ordinary skill in the art that other sources of organic material can also be used in the same HTTP 100. For example, many high moisture renewable fuel sources and non-renewable fuel sources such as coal may be used to generate power in the inventive HTPP 100. Waste water sludge will preferably be taken off the bottom of the existing WWTF gravity thickeners at approx 3% biosolids (BS) concentration. The sludge can be ground as necessary to improve pumpability, and then pumped at low pressure to the HTPP 100. The sludge is preferably centrifuged to approx 10% biosolids concentration. Filtrate water from the centrifuge is sent back to the WWTF headworks. The concentrated sludge is then pumped to combustor pressure via pump 260.

When the fuel to the SCWOR is sludge it is pre-heated by heater 265 to approx 200° C. before injection into SCWOR 110, which is preferably a hydrothermal transpiring-wall combustor (such as are disclosed in U.S. Pat. Nos. 5,558,783 and 5,384,051) where it is turbulently combined with a preheated mixture of superheated steam and compressed air. The combustor will normally operate at subcritical pressures (below the critical pressure of water), but may also be designed to operate above the critical pressure of water. Spontaneous oxidation of the sludge occurs upon mixing within the combustor. Superheated reaction products (CO₂, N₂, excess O₂, water vapor and inorganic residuals) exit the bottom of the combustor and enter the quench cooler 120.

The quench cooler 120 partially cools the stream, thereby forming a saturated 2-phase vapor-liquid mixture. This 2-phase stream then enters a gravity or brine separator 130 for separation into liquid and vapor streams. This gravity separator 130 operates below the local saturation temperature of water and will contain what will be referred to as brine, as it contains some dissolved inorganic salts. As shown in the embodiments of FIGS. 1 and 3-6, the hot liquid phase or brine leaves the bottom of the separator 130 at a lower exit portal 132 and then enters the line forming loop 1300, carrying with it all of the suspended and dissolved inorganic constituents of the sludge.

In the embodiment of FIG. 3-6, the stream in line 1300 passes through a steam generator 270, such as a shell & tube heat exchanger for example, before being recycled back to the quench cooler 120 via pump 121. The steam generator 270 is thus designed to extract useful heat from the liquid brine recirculation loop 1300. The brine circulation quench pump 121 supports the continued flow of brine in loop 1300.

As shown in FIG. 3-8, inorganic solids are continuously removed from the stream of loop 1300 via hydrocyclone filtration at filter 500, and then removed from the system via blowdown for solids dewatering and disposal at 505. A hydrocyclone 500 is optionally replaced with a filter or other means known in the art to separate and remove free solids from the liquid in brine recirculation loop 1300. “Blowdown” refers to a liquid stream leaving the process for disposal. This stream would contain any separated solids from the hydrocyclone or filter, but might only contain dissolved solids to control the total amount of dissolved solids in the brine recirculation loop. This technique is routinely used in steam boilers to prevent total dissolved solids from reaching saturation and precipitating out on the walls of the equipment as scale. The blowdown water containing the dissolved solids is then directed back to the WWTF headworks. This Blowdown is a small percentage of the total flow through the recirculation loop.

In the embodiment of FIGS. 1, 3 and 4 the hot vapor mixture of CO₂, N₂, O₂ and water vapor exits the 2-phase gravity separator 130 at exit portal 133 and enters a condenser 220, where the water vapor is condensed and separated from the non-condensable gases.

It should be appreciated that the condensed water output from condenser 220 at port 242 is generally free of inorganics and organics; it is essentially distilled water, but may require additional polishing. Such excess condensed water is drained from the process and returned to the WWTF, such as at moisture condenser 240, via outlet 242. The remaining condensed water is heated and vaporized for mixing with the compressor air (from compressor 3317) via valve 1403, prior to injection into the SCWOR combustor 110. Thus, a portion of this condensed water is optionally recycled back to the combustor or SCWOR 110 (via circulation pump 107) for liner transpiration via liner 115 at inlet port 1406 (where it is delivered outside the permeable-wall or transpiring wall 115.) However, the water before returning to the either the injector 1405 or the side port 1406 is preferably reheated by one or more injector trim heaters 1401.

Therefore, two 3-way flow control valves 1402 and 1403 are provided for dividing the total flow of compressed air and transpiration water to separate destinations. Such flow control valves might use multiple 2-way valves instead of a single 3-way valve to achieve same end. Flow control valve 1402 divides liquid transpiration water into two streams. One stream going to the boiler to be vaporized for use in transpiration service and the balance going to the boiler to be vaporized for use in injection/mixing service with the feed. Flow control valve 1403 divides the compressed air into two streams. One stream goes to the reactor annulus at port 1406 for use in transpiration service and the balance going to the feed injector 1405 for injection/mixing with the feed from pump 265. The injector trim heaters 1401 are also useful in reactor start-up and control.

In the embodiments of FIG. 1-4, the non-condensable gases are used to generate power in generation train 3000 by being fed to one or more gas expanders wherein they drive a rotary mechanism. Such expanders are generally, but not exclusively turbine devices. As shown in FIG. 1, in stage 3300 of train 3000 each of the air compressor stages 3317 are coupled in rotary motion to one or more gas expansion stages 3315 by a common drive mechanism 160. The exact nature of the drive mechanism will depend on the structure and type of the expander and compressor, which although both are preferably turbine devices, as other types of compressors known in the art can be deployed in the embodiments described herein. One or more of such coupled compressor-expander pairs or stages are arranged in a train of two or more pairs to achieve higher overall compression ratio and expansion ratio than possible with pair. Two or more compressor and expander stages may be coupled in rotary motion at different rotational speeds by means of a common gearbox, as done in integrally-geared compressors known in the art. The cooperative operation of the other stages of train 3000 is shown in more detail in FIG. 2. The non-condensable gases leaving the condenser 240 are heated in a pre-heater 3318 by heat from the hot brine recirculation loop 1450 and then reduced to atmospheric pressure via a multi-stage hot gas expander cascade train 3000. Each stage of the expander cascade drives one of the compressor stages. Should it be desired to recover carbon dioxide from this stream of non-condensable gases, it would best be done upstream of the high-pressure expander preheater at unit 245, wherein the carbon dioxide by removal is represent by the exciting arrow 246.

The power train 3000 preferably deploys 3 or 4 stages of compression with intercooling, while the expansion likewise requires 3 or 4 stages of expansion with interstage reheat. FIG. 2 illustrates a preferred aspect of the invention with three separate expander-compressor pairs 3100, 3200 and 3300 cascaded in series. In this aspect, heat from each compressor intercooler is used to heat and expand the non-condensable gases upstream of each interstage reheater. This reduces the total preheat required upstream of each stage of expansion, providing more efficient production of energy from the biomass feed. This allows each expander-compressor train to operate more closely to its optimum speed for maximum efficiency. Thus, at least 2 of the 3 coupled expander-compressor pairs 3100, 3200 and 3300 have at least one associated heat exchanger 3110 and 3210 (for 3100 and 3200 respectively) that receives the compressor output as a heat source and to increase the enthalpy of the exhaust of the preceding expander in the chain.

Thus, in operation the output gas from the first compressor 3117 is fed to the next compressor 3217 in pair 3200, and the output of compressor 3217 is feed to the next compressor 3317. An intercooler such as 3110 for compressor-expander pair 3100 cools the gas before the next stage of compression. However, the intercooler receives the cooler exit gas from each expander as the heat transfer fluid such that heat or enthalpy in the gas from compression is transferred to the gas before the next stage of expansion.

In addition, the input to the last expander 3115 in coupled compressor-expander pair 3100 is heated first by the output of compressor 3117 via air compressor intercooler 3110, which acts as a heat exchanger.

Further, the input of the second expander 3215 in coupled pair 3200 is heated first by the output of compressor 3217 via air compressor intercooler 3210 that acts as a heat exchanger.

In addition, heat from the brine separator 130 liquid effluent stream in line 1300 supplies additional higher temperature heat to the exhaust gases of an expander prior to a first or subsequent expansion stage downstream of s air compressor intercoolers. Thus, preferably as shown each of expanders 3150, 3250, and 3350 are thus associated with heat exchangers 3118, 3218 and 3318 which respectively receive either the re-circulating brine, or a heat transfer fluid heated there from, as a heat source to further increase the enthalpy of the exhaust of the preceding expander.

The final low-pressure expander-compressor pair 3100 is connected to a motor/generator 3001. During plant start up from a cold condition motor operation is generally required drive the air compressors. As the system comes up to temperature, the low-pressure expander will gradually supply power to the compressor and eventually produce enough power to generate surplus electric power to the grid. The intermediate-pressure and high-pressure expander-compressor trains 3300 and 3200 may or may not have a connected motor/generator 3002 and 3003 respectively.

While U.S. Pat. Nos. 5,485,728 and 5,000,099 similarly use a SCWOR in a power generation scheme they do not appear to teach or suggest the “brine” heat or the heat of compression is used to reheat the expanded gas before it is feed to the next turbine. These patents all refer to preheating the gas before the expander by extracting heat from a hot gaseous stream. The present invention extracts heat from the hot liquid recirculation stream 1300.

Thus, in the present invention the integrated combination of air compression, constant pressure hydrothermal combustion and gas expansion with energy recovery thereby completes a Hydrothermal Brayton Power Cycle.

As shown in FIG. 3-6, another aspect of the invention is the steam generator 270 located in the hot brine recirculation loop 1300, which generates steam supplying a conventional steam turbine system 300 for additional power recovery. The steam turbine 314 may drive a dedicated electric generator 312, or may be connected to the low pressure expander-compressor-motor/generator train via a conventional overrunning clutch. These alternative coupling means are designated 1450 in FIG. 5-6. The effluent from the steam powered turbine 314 then enter the steam condenser 311, which has a water cooling inlet 313. The steam turbine re-circulation pump 106 is used to return the output of the steam condenser 311 to the heat exchanger 220 that pre-cool that mixture entering the moisture condenser 240, while a second recirculation pump 105 returns the water exiting this heat exchanger 220 to the steam generator 270.

The total net power produced by the HTPP 100 is roughly evenly split between the expander-compressor cascade 3000 and the steam turbine system 300. Overall HTPP thermal efficiency is approximately 38% based on higher heating value of the wet feed. Thus, while the present invention will always incorporate a Brayton power generation cycle it may or may not include an optional Rankine (steam) co-generation cycle.

In FIGS. 4 and 6, an optional steam superheater 400 is disposed at least partially within the SCWOR 110 to further improve the efficiency of the steam turbine system 300. The superheater 400 acts as a heat exchanger that heats the output of the steam generator 270 before it reaches the steam turbine 314.

In another embodiment of the invention there is a mode of operation whereby a condenser 240 does need not be disposed in the vapor outlet from the brine separator 130 to directly inject the hot vapor mixture into the expander-compressor. These embodiments are illustrated in FIG. 5 and FIG. 6 by the optional bypass line 5001 having valves around the condenser 240, which allows HTPP operation without the condenser in the loop. The reason for condensing and cooling the hot vapor exhaust stream is to cool the gas to facilitate removal of CO₂ from the high-pressure exhaust gas stream, which is most easily done cool.

In other aspects of the invention, it may be preferable to provide for in-situ cleaning of the combustor liner and feed injector by injection of a suitable cleaning agent into the feed injector assembly and into the annular space between the pressure vessel wall and permeable liner of the SCWOR 110. Water treatment systems as known in the art to control corrosion and fouling of process equipment.

Further, in the embodiments shown in FIGS. 5 and 6 a dashed line 166 is intended to illustrate the optional gear box or clutch coupling between the generators 3001 and 312, or a common shaft to a single generator.

It should be appreciated that in alternative embodiments the oxidizer to the SCWOR 1000 may be air, oxygen enriched air, or oxygen. Air separation technology may optionally be installed upstream of the SCWOR 110 to separate air into oxygen-rich and nitrogen-rich streams. The nitrogen-rich stream may optionally be used to drive a gas expander as part of the power generation train 3000. Such oxidizer or oxygen enriched stream may or may not be mixed with the transpiration water entering at portal 1406.

In power train 3000, additional motors 3002 and 3003, may or may not be required at all depending on the application. For example, the motor 3003 might be required for start-up, but then once the system is up to pressure and temperature, the compressor is driven solely by the expander. It is preferable to start the system up without using motors on the higher pressure expander-compressors. A clutch coupling 3116 and 3216, typically an overrunning clutch, is deployed such that when the expander-compressor comes up to speed it automatically disengages from the motor 3003, allowing the motor to be switched off. Such clutches are commonly employed in industry. Although a hydrodynamic centrifugal or axial type compressor is shown in the diagram, for smaller plants a reciprocating compressor as known in the art may also be similarly employed in which all stages are driven via a common drive mechanism and motor/generator. Likewise, although hydrodynamic centrifugal or axial gas expanders are shown in the diagram, for smaller flows a reciprocating or other positive displacement type expansion engine may also be similarly employed whereby all stages of expansion may be connected via a common drive mechanism.

In other embodiments of the invention the air compressor stages may be driven independently from the gas expander stages. Gas expander stages are capable of generating mechanical power to directly drive electric generators, air compressors, pumps, chillers or any other type of driven equipment.

FIG. 7 illustrates yet another embodiment of the invention in which the fluid phase the output of the gravity or brine separator 130 is directed from the bottom thereof at portal 132 through level control valve 706 causing a pressure drop with expansion device or flash drum 701. The flash drum 701 generates steam and condensed water having some dissolved or suspended solids. In addition, output gas of the SCWOR 110 also exits the gravity separator 130 at the upper portal 133, and is directed in line 710 toward a system pressure control valve 705. Line 710 then directs this gas to the input port 3712 of the first or higher pressure expander 3710, which is mechanically coupled to a second or lower pressure expander 3720.

The low pressure output gas exiting portal 733 of the flash drum 701 is feed to the input port 3722 of the second or lower pressure expander 3720 via line 720. The lower pressure expander 3720 can also receives at inlet port 3722 the output from exit portal 3711 of the higher pressure expander 3710, which is mixed into line 720. As in other embodiments, the rotary mechanical coupling from the expanders 3710 and 3720 drives generator 3710 to produce electric power or other useful energy. It should be appreciated that this embodiment does not require to expanders, as the gas output of either the gravity separator or flash drum can drive a single expander, with the gas output of the other device being used to power an unrelated expander, such as for example in the other embodiments of the invention.

U.S. Pat. No. 4,819,437 (issued to Dayan on Apr. 11, 1989), which is incorporated herein by reference, also discloses a process for converting thermal energy to work in which a solution is decompressed, by means of an expansion device, such as a flash drum, in which the exiting vapor mixture is then expanded in a turbine to produce additional work.

Liquid output from the bottom of the flash drum 701 will contain a mixture of suspended and dissolved solids. This liquid stream is preferably separated in brine loop 1300′ by hydrocyclone filtration at filter 500, within recirculation or return to loop 1300′. The liquid effluent from the solid separator or filter 500 thus returns to the quench cooler 120, via a brine circulation pump 121. However, the hot brine may be used in heat exchanger 7401 to pre-heat the feed from pump 260 before it reaches the main heater 265. loop 1300′ returns water back to the gravity separator 130, preferably by mixing in quench cooler 120 with the direct effluent from SCWOR 110.

It should also be understood that in alternative embodiments of the invention, the output of the SCWOR 110 can be cooled by other means than the quench cooler, with the same effect of the output thereof entering the gravity separator. In such embodiments the output of the gravity circulator can return thereto via the brine circulation loop 1300 or 1300′, without the need to enter an equivalent cooling means.

Water from the gas streams or steam that drives the expanders can also be returned in a re-pressurized state to the SCWOR 110 as in other embodiments. The low pressure side output at portal 3721 of the low pressure expander 3720 is directed to a moisture condenser 7240. The condensate there from is stored in a condensate recovery tank 7241. Liquid condensate is drawn from the bottom of this tank and optionally feed by a pump 261 back to the injector 1405 or between the transpiring wall and inner chamber wall of the SCWOR 110, but preferably after being re-heated and re-pressurized via the high pressure heaters 707 and 708 respectively. The output of a second feed air compressor 702, which is driven by motor 703, is directed toward valve 1407 and 709 to pressurize and drive the water or steam generated by heaters 707 and 708.

The output of fluid from heater 707 is controlled by valve 709 to direct water to the SCWOR chamber or reactor annulus at port 1406 for use in transpiration service. The output of fluid from heater 708 is controlled by valve 1407 to direct water to the feed injector 1405 for injection/mixing with the feed from pump 265.

Make up water is optionally fed to the condensate separator or recovery tank 7241 via port 7012. The condensate separator or recovery tank 7241 externally vents non combustible exhaust gases at line 7301.

In the embodiment of FIG. 8, which is a variant on the embodiment of FIG. 7, an optional steam superheater 400 is disposed at least partially within the SCWOR 110 to further improve the efficiency of the generation of electric power at generator 3730, by pre-heating the gas output of the gravity or brine separator 130 in line 710 before or after it reach pressure control valve 705. Thus, the output of the gravity brine separator 130 travels via line 411, and returning to feed the expander 3710 via line 412. Alternatively, the superheater 400 can receive and pre-heat gas exiting the flash drum 701 that travels in line 720, as shown by broken lines at 411 and 412.

FIG. 9 illustrates a common and representative structure for a gravity separator 130. The gravity separator 130 has an inlet port 131 for receiving effluent, such as from the quench cooler 120 of the SCWOR 110. The influent hits deflection plate 134 which directs liquid downward toward the bottom, where upon prompt gravity separation it can exit via portal 132. Mist and vapor that expands upward in the separator 130 reaches a mist removal device or water vapor coalesce means 135 situated below the upper vapor exit portal 133. The mist removal device 135 is optionally a mist mat, vane pack, hydrocyclone and the like, so that liquid from the mist is collected and flows downward, and the vapor phase exits at portal 133. U.S. Pat. No. 7,654,397 (issued to Allouche on Feb. 2, 201), which is incorporated herein by reference, also discloses the construction of a particular type of gravity separator that separates a liquid phase and a gas phase from a multiphase fluid mixture.

While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be within the spirit and scope of the invention as defined by the appended claims. 

We claim: 1) A power generating plant that comprises: a) super critical water oxidation reactor (SCWOR) having at least one first feed port for reactants, a second feed port to receive a portion of the effluent there from after re-pressurization, and an exit port for exhaust of effluent, b) a gravity separator having; i) an inlet for receiving the exhaust of the SCWOR, ii) at least one gas outlet, iii) at least one fluid outlet for hot fluid brine, iv) at least one fluid inlet for brine that is cooler than that exciting at the at least one outlet for hot fluid brine, c) a brine circulation loop for routing heated fluid brine from the at least one outlet of the gravity separator and returning it to the at least one fluid inlet port thereof, d) at least a first pair of an air compressor and an expander in a cascade arrangement and coupled in rotary motion by a common axial drive mechanism, wherein the hot exhaust gas from the at least one gas outlet of the gravity separator enters the expander to drive the common axial drive mechanism, wherein re-pressurized gas exhausted from the air compressor is returned to the SCWR at the second feed port thereof, e) at least one heat exchanger that is coupled to said brine circulation loop to provide for reheating of gas prior to entry into an expander, f) at least one of a motor and motor/generator with a rotary coupling to the common axial drive mechanism of the air compressor-expander pair, wherein the rotary motion of the common axial drive mechanism supplies mechanical power driving the generator for at least one of electric power generation and driving the air compressor. 2) A power generating plant according to claim 1 that further comprises; a) a second pair of an air compressor and an expander coupled in rotary motion by a common axial drive mechanism, b) a second heat exchanger that is coupled to the exhaust of a compressor to receive energy there form for re-heating a fluid passing there through, c) wherein the exhaust from the expander of the first pair is reheated in the second heat exchanger before entering the expander of the of second pair, d) wherein the rotary motion of the common axial drive mechanism of at least one of the first and second expander-compressor pair supplies mechanical power driving the generator for at least one of electric power generation and driving the air compressor. 3) A power generating plant according to claim 2 further comprising a third heat exchanger that is coupled to said brine circulation loop to receive energy there form for re-heating a fluid passing there through. 4) A power generating plant according to claim 1 that further comprises a quench cooler disposed to receive the effluent from the exit port of the SCWOR fluid for mixing therein with fluid received from the brine circulation loop and returning the mixture thereof to the gravity separator at the at least one fluid port thereof. 5) A power generating plant that comprises: a) super critical water oxidation reactor (SCWOR) having a feed port for reactants and an exit port for exhaust, b) a gravity separator having; i) an inlet for receiving the exhaust of the SCWOR, ii) at least one gas outlet, iii) at least one fluid outlet for hot fluid brine, iv) at least one fluid inlet for brine that is cooler than that exciting at the at least one outlet for hot fluid brine, c) a brine circulation loop for routing heated fluid brine from the at least one outlet of the gravity separator and returning it to the at least one fluid inlet port thereof, d) at least one expanders coupled in rotary motion to a generator, wherein the at least one expander receives and is driven by gas exhausted from the at least one gas outlet of the gravity separator, e) a steam generator located in the hot brine recirculation loop that generates steam which it then provides a steam turbine system for power generation than that produced by the at least one expander. 6) A power generating plant according to claim 5 that further comprises a quench cooler disposed to receive the effluent from the exit port of the SCWOR fluid for mixing therein with fluid received from the brine circulation loop and returning the mixture thereof to the gravity separator at the at least one fluid port thereof. 7) A power generating plant that comprises: a) a super critical water oxidation reactor (SCWOR) having at least one first feed port for reactants, a second feed port to receive a portion of the effluent there from after re-pressurization, and an exit port for exhaust of effluent, b) a gravity separator having; i) an inlet for receiving the exhaust of the SCWOR, ii) at least one gas outlet, iii) at least one fluid outlet for hot fluid brine, iv) at least one fluid inlet for brine that is cooler than that exciting at the at least one outlet for hot fluid brine, c) a flash evaporator for receiving a liquid solid mixture from the bottom of the brine separator, the flash evaporator having an upper gas outlet portal and a lower fluid outlet portal, d) a brine circulation loop for routing fluid brine from the lower fluid outlet portal of the flash evaporator and returning it to the at least one fluid inlet port of the gravity separator, e) a first expander coupled in rotary motion to a generator, wherein the first expander receives and is driven by gas exhausted from the at least one of the one gas outlet of the gravity separator and the upper gas outlet portal of the flash evaporator. 8) A power generating plant according to claim 7 that further comprises a quench cooler disposed to receive the effluent from the exit port of the SCWOR fluid for mixing therein with fluid received from the brine circulation loop and returning the mixture thereof to the gravity separator at the at least one fluid port thereof. 9) A power generating plant according to claim 7 that further comprises a second expander coupled in rotary motion to drive the generator, wherein the first expander receives and is driven by gas exhausted from the at least one of the one gas outlet of the gravity separator, and the second expander receives and is driven by a mixture the upper gas outlet portal of the flash evaporator plus the exhaust from the preceding expander. 10) A power generating plant according to claim 8 wherein the first expander has an outlet port for exhausted lower pressure gas, and the second expander is in fluid communication with the outlet port of the first expander to receives and be driven by the exhausted lower pressure gas. 11) A power generating plant according to claim 10 that further comprises a quench cooler disposed to receive the effluent from the exit port of the SCWOR fluid for mixing therein with fluid received from the brine circulation loop and returning the mixture thereof to the gravity separator at the at least one fluid port thereof. 12) A power generating plant according to claim 10 that further comprises a superheater disposed at least partially within the SCWOR, wherein the superheater receives gas from a gas outlet of at least one of the gravity separator and the flash drum and returns hotter gas to the first expander. 13) A process for generating power, the process comprising the step of: a) oxidizing an aqueous suspension of combustible matter in a SCWOR having a transpiring wall to generate hot effluent exiting there from, b) cooling the hot effluent by mixing with an aqueous media to form a two phase brine, c) extracting gas from the 2 phase brine to form a liquid brine, d) driving a generator with the extracted gas, e) re-circulating at least a portion of the liquid brine as the aqueous media. 14) A process for generating power according to claim 13 wherein gas is extracted from the liquid brine in a first stage and thereafter in a second stage, wherein the gas extracted in the first stage is at a higher pressure than the gas from the second stage, and the gas from the first stage is directed to a first expander and the gas from the second stage is directed to a second expander. 15) A process for generating power according to claim 14 wherein the first and second expander are mechanically coupled to drive a common generator and gas exhausted by the first expander also drives the second expander. 16) A process for generating power according to claim 13 further comprising extracting heat from the liquid brine before said step of re-circulating. 17) A process for generating power according to claim 16 wherein the heat extracted from the heat from the liquid brine pre-heats the aqueous suspension before it is oxidized in the SCWOR. 18) A process for generating power according to claim 13 further comprising the steps of a) condensing water from gas that is exhausted from the first expander, b) returning said condensed water to the SCWOR. 19) A process for generating power according to claim 18 wherein the water returned to the SCWOR is at least one of: a) mixed with the aqueous suspension that is oxidized; and b) injected between an inner wall of the SCWOR and the transpiring wall. 20) A process for generating power according to claim 13 wherein gas is extracted from the liquid brine in a first stage and thereafter in a second stage, and the first extraction stage is in a gravity separator and the second extraction stage is in a flash drum, wherein an intermediate brine flows from an exit port of the gravity separator to an inlet port of the flash drum. 